Comparisons of an asteroid and the Martian moons

. Three irregularly shaped, cratered objects, each about the same size, are shown at the same scale and nearly identical lighting conditions. They are Phobos (lower right), the largest moon of Mars, Deimos (lower left), the other Martian moon, and the asteroid 951 Gaspra (top) which is about 17 kilometers across. The Phobos and Deimos images were obtained from one of the Viking orbiter spacecraft in 1977; the Gaspra image was taken from the Galileo spacecraft in 1991 on its way to Jupiter. (Courtesy of NASA and JPL.)